1. Field
This invention relates to golf clubs, and more particularly to golf club irons, having a dual counterweight which improves the performance of miss hits on the club face and also reinforces the club face for center hits.
2. State of the Art
A large number of different golf club iron sets are known. These correlated sets of golf clubs have club striking faces with increasing angles of attack to loft a ball a desired distance. The club heads are also increasingly weighted, and the shafts are decreasingly shortened to maintain consistent swing momentum so that each club swing, if properly hit, increases the distance the golf ball travels by approximately 10 yards. For example, in a correlated set, each club head weight generally increases approximately 7 grains per increase in club number. However, each shaft length incrementally decreases about 1/2 inch for a steel shaft per increase in club number (If lighter weight shafts made of graphite, or similar materials are employed, each shaft will be lengthened approximately 1/2" so that the shaft has approximately the same weight as a steel shaft). Shaft types and lengths vary depending upon the swing of a golfer. For example, the majority of golfers fall into the average swing category, and have a 65 to 85 mph swing requiring a shaft with a low flex point and a 4.0 torque rating. Conversely, professional golfers having a 100 to 115 mph swing require a shaft with a mid flex point with a 2.0 torque rating.
The angle of the club face also increases per increase in the club number to add loft to the flight of the golf ball. The weighted center of gravity of the club also moves up per increase in club number. A typical set has the following specifications:
__________________________________________________________________________ SPECIFICATIONS Club 1 2 3 4 5 6 7 8 9 __________________________________________________________________________ Loft 16.degree. 18.degree. 21.degree. 24.degree. 28.degree. 32.degree. 36.degree. 40.degree. 44.degree. Lie* 56.degree. 57.degree. 58.degree. 59.degree. 60.degree. 61.degree. 62.degree. 63.degree. 64.degree. Weight** 223 240 247 254 261 268 275 282 289 __________________________________________________________________________ *Lie = plus or minus 0.5 degrees **Weight = plus 2 gr. or minus 2 gr.
A few golf club irons are designed to enable a golfer to off center hit the ball on the club face and maintain shot alignment. Thompson, U.S. Pat. No. 3,845,960, and Imai, U.S. Pat. No. 4,322,083, are examples of sole reinforced iron clubs which add mass along the sole of the club to optimize distance. Although distance is increase, heel or toe off center hit shots do not maintain shot alignment. Nor do shots hit on the upper unreinforced face of the club maintain distance.
For those golfers who consistently hit their shots along the toe of the club, a number of toe weighted clubs have been designed: Lamanna, U.S. Pat. No. 4,715,601, Solheim, U.S. Pat. No. 3,655,188, and Campau, U.S. Pat. No. 4,420,156.
Solheim, U.S. Pat. No. 4,621,813, discloses a correlated set of golf clubs with back cavities, the heads of which each contain (1) a sole including a trailing edge which is indented toward the striking face a distance of at least 1/16 of an inch, and (2) a lower back surface adjacent the indented trailing edge sloping upwardly and inwardly from the indented trailing edge toward the striking face. This configuration allows the club head material which would otherwise be located in the indented areas to be redistributed in the heel and toe portions of the club heads. The redistributed head materials increase the mass concentrations in the heel and toe areas which improves the resistance to twisting of the club heads upon off-center heel and toe impacts with the golf ball. Another example of a back cavity club with heel and toe reinforcement is Lockwood, U.S. Pat. No. 3,751,035. The center cavity club designs maintain alignment, but do not allow an off center hit shot to maintain consistent distance. Nor do center hit shots achieve optimum distance as the center face of the club does not have sufficient mass behind it.
McNally et al., U.S. Pat. No. 5,026,056, discloses another heel-toe balancing club. McNally et al. discloses a correlated set of golf clubs of the iron type in which each club head has a cavity formed in the back surface thereof with specially configured weight pads formed integrally within the back cavity. The weight pads are so configured and positioned within the confines of the back cavity as to create desired heel-toe balancing of each club head wherein each club head's center of gravity is physically centered, both horizontally and vertically of the club head, behind the visually-perceived optimal striking point, i.e., the apparent visual center of percussion of the club's striking face relative to the golf ball at address. This configuration is designed to provide better club balance, and minimize misdirection of heel or toe off center hit shots. Other examples of heel-toe balancing clubs are: Reymann, Jr. et al., U.S. Pat. No. Des. 269,101, and Solheim, U.S. Pat. No. Des. 276,644.
These cavity backed clubs do not provide a solid mass behind the club face center to maximize hitting distances. To overcome this lack of center of mass, the Merit Fusion/Nicklaus N1 provides a set of correlated golf clubs with an iron weight bar placed within the inside of the back cavity which can be adjusted vertically to promote vertical balancing for an exact center of gravity as well as provide additional mass behind the club face. MacDonald, U.S. Pat. No. 4,326,326 is another example of a lead insert golf club head positioned directly behind the center of the intended striking surface to improve distance. Other examples of center reinforced golf club heads are: Winquist, U.S. Pat. No. 3,814,437, Kobayashi, U.S. Pat. No. Des. 267,965, and Pace, U.S. Pat. No. Des. 268,775. Unfortunately, these center reinforced cavity configurations also raise the center of gravity of the club face, thereby reducing the mass along the lower center of the club face proximate the sole where maximum leverage striking force for an iron shot is delivered. Indeed, the Pace design actually raises the center of gravity.
Other patents of interest are: Solheim, U.S. Pat. No. 4,512,577, discloses a set of correlated golf clubs, the heads of which are provided with a narrowed neck connecting the main body of the club head to the hosel. The midsection of the neck has a cross section of maximum dimension less than the diameter of the hosel so that, when the main body of the club head twists under impact with a ball, the narrowed neck will function as a torsion bar with twisting tension occurring in the midsection. In that manner, the twisting motion of the main body is uncoupled from the hosel and shaft to provide a more forgiving shock absorbing club head in the event an iron shot is miss hit. This shock absorbing feature does not give consistent distance to a miss hit ball.
Moser, U.S. Pat. No. 3,250,536, is an example of a sand wedge with a reinforced weighted club having a different density filling material filling a cavity in the back of the club to balance the club.
There thus remains a need for a rear cavity weighted club which maintains a low center of gravity while providing additional mass behind the center of the striking surface of the club to optimize shot distance and alignment even though the shot is off center hit near the toe, heel, or upper segment of the club face. The golf club set described below provides such an invention.